This proposal requests support for the purchase of the Beckman Coulter GalliosTM Flow Cytometer for placement in the Flow Cytometry Core Facility at the University of North Carolina at Chapel Hill. This instrument will complement existing instrumentation in the Core which is the central flow cytometry facility for researchers a the university. The Gallios will be primarily used for the detection, enumeration and characterization of sub-micron particles, specifically microparticles (MPs). MPs are sub-micron membrane vesicles that are released from cells, including platelets, monocytes, red blood cells, endothelial cells and tumor cells, upon activation or apoptosis. MPs are postulated to play a role in a number of biological and pathological processes, such as the activation of coagulation, cancer associated thrombosis, tumor metastasis and potentially, angiogenesis. MPs may also serve as sensitive biomarkers in various disease states. There are a number of investigators in multiple departments that are currently studying the role of MPs in health and disease. The ability to reliably detect MPs would be a great asset and help advance their research. In addition, the unique forward scatter detection design that allows MP measurements, also allows investigation of submicron bacteria that are involved in the pathology of a number of infectious diseases. The feature of the Gallios that sets this flow cytometer apart from all other currently available flow cytometers is its ability to resolve particles down to 0.404 m in diameter. The Gallios is superior to any flow cytometry machine on the UNC campus or surrounding region with regard to MP resolution, characterization and enumeration. When compared to other similarly equipped flow cytometers in the market, this instrument boasts greater resolution, sensitivity and specificity as well as a lower level of electronic noise. Detailed plans for instrument usage by different research groups, administrative and technical responsibilities, and user access and training have been developed and are outlined in the application.